The present invention relates to a flame retardant resin composition, and more particularly to a silicone resin acting as a flame retarder which provides a flame retardancy to non-silicone resin composition containing an aromatic ring
Flame retardant resin compositions have been widely used for electric and electronic components and devices, building materials, automobile parts, daily necessities and the like. In general, such base material resin compositions are added with an organic halogen compound or added with both an organic halogen compound and antimony trioxide so that the base material resin compositions are provided with the flame retardancy. Such the flame retardant resin material has a disadvantage that burning this flame retardant resin material causes generation of harmful halogen gases.
It has been known by one skilled in the art that in order to avoid the above disadvantage it is effective to add the base material resin composition with silicone thereby to provide the flame retardancy to the base material resin composition without generation harmful halogen gases when burning.
Silicone (organopolysiloxane) comprises at least any of the following four units (M-unit, D-unit, T-unit and Q-unit). Silicone resin in general includes at least any of T-unit and Q-unit. ##STR1##
In the Japanese laid-open patent publication No. 1-318069, it is disclosed that a thermoplastic material is provided with flame retardancy by powdered polymer mixture which comprises a thermoplastic polymer and a silicone resin (R.sub.x Si(OR').sub.y O.sub.(4-x-y)/2) consisting of all of the above four units and also having either alkoxyl group or hydroxyl group.
In the Japanese laid-open patent publication No. 2-150436, it is disclosed that a thermoplastic material is provided with a flame retardancy by a mixture of the normal silicone powder such as dimethyl-silicone, metal hydroxide and zinc compound.
In the Japanese patent publication No. 62-60421, it is disclosed that a thermoplastic non-silicone polymer is provided with flame retardancy by polysiloxane containing 80% by weight or more of T-unit represented by RSiO.sub.1.5. Particularly, it is preferable for providing the flame retardant to the polymer component that the molecular weight of the polysiloxane resin is not less than 2000 and not more than 6000 and R in the formula comprises not more than 80 mol % of phenyl group and the remaining percents of methyl group.
In the Japanese patent publication No. 3-48947, it is disclosed that a thermoplastic material is provided with a flame retardancy by a silicone resin, particularly a MQ silicone which comprises M-unit of R.sub.3 SiO.sub.0.5 and Q-unit of SiO.sub.2, silicone and Group IIA metal salts.
In the Japanese laid-open patent publication No. 1-318069 or No. 2-150436, the use of normal silicone resin alone results in an insufficient flame retardancy, for which reason flame retarder such as halogen compounds, phosphorus compounds, metal hydroxide may be used and added.
The specific silicone resins disclosed in the Japanese patent publications Nos. 62-60421 and 3-48947 have to be added at a large amount for obtaining a sufficient flame retardancy.
In the Japanese patent publication No. 62-60421, 10 parts by weight to 300 parts by weight of silicone resin, preferably 20 parts by weight to 100 parts by weight, are added to 100 parts by weight of non-silicone resin for flame retardancy. It is however disadvantageous that addition of such large amount of silicone resin results in remarkable deterioration of moldability and mechanical strength of the resin composition.
In the above circumstances, it had been required to develop a flame retardant resin composition having a high flame retardancy with addition of a small amount of silicone resin, and also having high moldability and mechanical strength.